Spray coating electrode structure



Nov. 28, 1950 R. H. STONE 2,531,542

SPRAY COATING ELECTRODE STRUCTURE Filed Dec. 5, 1945 IN VEN TOR. ROBERT I4. 3 TONE F1 G. 6 FIG. 9 FIG. 5'

Patented Nov. 28, 1950 2,531,542 SPRAY ooa'rmo ELECTRODE STRUCTURE Robert H. Stone, Indianapolis, Ind., assignor, by

mesne assignments, to Ransburg Electra-Coating Corp., Indianapolis, Ind., a corporation of Indiana Application December 3, 1945, Serial No. 632,473 9 Claims. (or 91-18) This invention relates to an improved electrode structure for use in electrostatic apparatus and which is particularly useful in spray coating of surfaces in an electrostatic field.

It is an object of the present invention to provide an electrode structure which is easily assembled and disassembled.

Another object is the provision of an electrode frame for holding ionizing electrodes under tension.

Another object is the provision of ionizing electrodes held out of the plane of their supports.

Another object is the provision of means for maintaining L-shaped ionizing electrodes out of the plane of their supports.

Another object is the provision of an electrode which extends into at least two planes and which is adjustable.

A further object is the provision of a solderless means for positively securing ionizing electrode wires under tension.

In accordance with one feature of the present invention, I provide an electrode frame composed of a plurality of removably coupled bars carrying ionizing electrodes. My electrode frame provides a structure which is resistant to twisting and which can be easily and quickly assembled and disassembled for a shipment, replacement or repair, without the necessity of special tools or equipment and should a part of the electrode structure become unfit to use, the part can be easily and accurately replaced by a prefabricated part without disturbing the arrangement of the entire structure.

In accordance with another feature of the invention, the ionizing electrodes, in the form of line wires, are carried by the electrode frame upon resilient members connected thereto which maintain the wire spaced during operation. Preferably the resilient members carry the wires out of the plane of the electrode frame so as to eliminate the electrostatic shielding action thereof, and reduce or eliminate the deposition of coating material on the frame during spraying operations. The provision of such resilient members has the further advantage of extending the useful life of the electrode wires by reducing or eliminating the possibility of breakage due to vibration or other accidental or operating conditions, and maintaining the wires taut by taking up play due to stretching of the wires in operation. The wires may all be positioned at the proper equal distance from the article to be coated. Also, the tendency of the electrode wires to vibrate under electrical impulses or air flow encountered in operation is reduced. The degree of strain on the wires also may be easily regulated, and an electrical connection between the wire and the frame is assured at all times. Also, no predetermined length of wire is required. Furthermore, the provision of said resilient tensioners removably secured to the removably coupled frame provide a structure which may be readily changed in size, shape or arrangement, as the various parts are interchangeable and may be employed in various combinations.

The invention will be described in greater detail in connection with the accompanying drawings in which are illustrated preferred embodiments of the invention by way of example and wherein:

Figure 1 is an end view of an electrode structure embodying the invention,

Figure 2 is a side view of Figure 1,

Figure 3 is a side view partly in cross-section of a detail of the electrode frame structure,

Figure 4 is a side view of a detail of a modified electrode structure,

Figure 5 is an end view of a detail of a modified electrode structure,

Figure 6 is a fragmentary cross-sectional view of a modified support for the electrode structure,

Figure '7 is a side view partly in section of a preferred ionizing wire support,

Figure 8 is a side view partly in section of another embodiment of the wire support, and

Figure 9 is a cross-sectional view of a further modification of the wire support.

Referring now to Figures 1 and 2 there is shown a pluralit of supports I constructed of a suitable insulating material, such as Bakelite, fastened at their upper ends in any suitable manner to the top of a spray booth 2' and having press fitted metal sleeves 2 at their lower ends which receive metal bars 3 held therein by a screw thread connection or the like. In the modification shown each electrode frame 4 and 5 has four socket shaped members 8, 1, 8, and 9 which provide coupling means at the ends which are alike in construction so that only one of them will be described in detail.

The socket member 6 at its lower end has a conical counterbore ll (Figure 3) terminating in a shoulder I2, and a bar l3 of the electrode frame 5 is received therein. A sleeve M in the counterbore ll surrounds the rod l3 and a nut l5 threaded upon the lower end l6 of the socket member engages the sleeve and forces it against the tapered counterbore H thus contracting the sleeve and causing the shoulder l1 thereon to bite into the rod l3 to form a groove l8. and prevent withdrawal of the bar. The bar 3 is similarly secured in the upper end IQ of the fitting 8. The electrode frame 5 is made up of a bar l3 extending vertically from the socket member 8 and secured at its lower end in socket member 8, a horizontal bar 2| secured in the le 22 of the socket member 8 having at its end the socket member 1, the bar 23 secured at its ends in socket members 8 and 8, and bar 24 secured at its ends in socket members I and 8. The number of bars and couplin: member may be less than four, for example. when L-shaped bars are employed, and the invention is not limited to the specific frame structure shown in the drawing. As illustrated in Figure 1. two electrode frames 4 and 5 may be employed, between which passes the suspended grounded article 25 to be treated on a suitable conveyor 29, and if desired the frames may be secured together, as by one or more U-shaped stay bars 26 which has its ends secured in lower socket member 8 and 8' of the respective electrode frames. The electrode frames are connected in any suitable manner to a source of high electric potential 21, the other output terminal thereof being grounded. A spray device 28 is suitably located and supported to introduce a stream of finely divided material for coating the article, as for example, like the disclosure in Patent 2,247,963 issued July 1, 1941 to Harold P. Ransbur et al.

The construction of the electrode frame is such that the bars I3, 2|, 23, and 24 are cut to predetermined lengths, and when applied to the respective socket members and locked therein, there will be formed an electrode frame of predetermined size because the shoulder |2 limits the overlap of rod received within the socket member. The electrode frame may be assembled using only a wrench. The bars can be removed readily for cleaning or replacement. The frames can be transported in a knock-down state, ready for assembly. The electrode frame is resistant to torsion at the joints.

Where it is desired to unite the electrode frames at the top instead of at the bottom, I employ elbow members 30 at the bottom (Figure 4) in place of coupling members 8 and 8. The top coupling members 6 and l are bored at 3| (Fig. 5) to receive a tie rod 32 held therein by a set screw 33, and coupling member 6' of the adjacent frame 4 is similarly bored to receive the other end of rod 32. This construction provides for adjusting the space between the electrode frames 4 and 5 by releasing set screw 33, moving the frames along rod 32. and tightening the set screw in the adjusted position.

Where a non-rigid detachable support is desired for the electrode frames, the rod 3 may be substituted by a stem 35 (Figure 6) welded in a shank 36 of a buckle 31 having a hook portion 38 engaging a screw eye 39 received in insulator I. v

A spring pressed detent or bolt 4| is provided to close the opening in the hook. Each coupling 6 and I may be provided with the hook arrange. ment described so that the electrode frame may be readily removed from the insulator supports.

Referring to Figures 1, 2, and 7, a tensioner arm 45 preferably made of spring steel or similar material has a hole 46 at one end through which passes a bolt 41 receiving the washer 48 on one side and nut 49 on the other. The tensioner arm 45 preferably is positioned at an angle of about 45 to the plane of the electrode frame, and extends into the space between the frames 4 and 5. The bolt 41 passes through a hole 5| in bar 2|,

with the angular end 52 of the tension arm engaging the side of the bar, and is held in position by a flat washer 53 and lock nut 54 on the end. At its opposit end 58 there are sharp edge tabs 51 and 58 on either side of a hole 53 which preferably are struck out from the strip at a, relatively sharp angle. A similar tensioner arm 45' is secured to the lower bar 23, and a fine wire 5| is secured between the tensioners 45 and45' by passing one end of the wire through hole 58in tensioner 45 and wrapping that end about the tabs 51 and 58, then passing the opposite end through the hole in the opposite tensioner 45' and wrapping the end about the tabs thereof. Wrapping of the wire around the tabs forces it into the relatively sharp angle between the tabs and strip and positively holds the wire against slippage. The degree of tension desired may be placed on the wire by deflecting the arms 45 and 45 to accommodate the length of wire.

Any desired number of wires 6| upon the tensioners 45 and 45' may be provided. By drilling holes at suitable intervals in the rods 2| and 23, the spacing of the electrode wires 6| may be predetermined. Also, if desired, bottom electrode wires 65 may be provided between the frames 4 and 5 secured on similar tensioners thereon to provide a U-shaped electrode.

If desired, the cross wires 65 may be located at the top of the electrode frame to provide an inverted U-shaped electrode, in which case I prefer to employ the modification of electrode frame described in connection with Figures 1, 2, 4, and 5 as this allows an article supported at the bottom to be passed between the frames. Also, it will be understood that an L-shaped electrode structure may be provided by omitting the electrode wires on one of the frames.

In the modification illustrated in Figure 8, the tensioner arm 10 has a doubly bent end portion II which is rounded to accommodate the bar 2|, and is clamped about the bar by a bolt 12 and nut 13. A tab 14 is located at the rounded portion and may be formed by striking up the metal of the arm. The opposite end of the tensioner arm, is curved at 15, the end continuing in a re.- verse curve I6 to provide an extension 11 having a slot 18 therein. The wire 6| passes through guide slot 18, over the curved end 15 and is received in a link or buckle hooked over tab 14, the end of the wire being laced in a figure eight through suitable openings in the buckle to hold it against slipping. The holes in the buckles are sharp edged and are of such size and so spaced as to positively resist slippage of the wire therethrough. This construction also has the advantage that a sharp curvature of the wire at I1 is avoided, so that breakage of the wire at this point is obviated.

If desired, the extension I1 and reverse curve portion 16 may be omitted and a guide groove or kerf can be suitably formed in the curved portion 15 of the arm 10 to position and guide the wire 6|.

In the modification shown in Figure 9, a sleeve has a pin 86 therethrough and a double hook 81 has one end received around bar 2| and the opposite end engages around pin 86. An extension coil spring 88 engages pin 86 by a hook portion 89 at one end, and the opposite end 8| engages a link 92 through a suitable hole therein. The wire 6| is interlaced through the holes 54, 95 in the link or buckle 92 and is thus held under suitable tension by the spring 88. The opposite end of the wire may be similarly secured to the electrode frame. This construction has the advantage that a predetermined length of the wire may have the opposite ends secured to links 80, and it is only necessary to hook the hooks 81 over the proper electrode bars to position and tension the electrode wires on the frame. Also the sleeve serves to protect the spring from becoming coated in the coating operation.

The diameter of the electrode wire 6| preferably is on the order of about 10 mils, although the invention is not limited to any particular size of wire. Various modifications may be made in the invention without departing from the spirit or scope thereof.

I claim:

1. In electrostatic coating apparatus, a pl-urality of socket members having tapered end bores terminating in shoulders, a plurality of bars having their 'ends received in said bores abutting said shoulders, sleeves surrounding the ends of said rods and having internal steps, nuts threaded on the ends of said socket members engaging said sleeves to force said sleeves into said bores and cause said steps to bite into said bars, and a plurality of ionizing wires extending between said bars.

2. In electrostatic coating apparatus, an electrode frame, resilient arms secured to said frame and extending out of the plane of said frame, and ionizing wires secured to said resilient arms and extending across said frame.

3. In apparatus for electrostatically coating a surface, means for supporting said surface, means for supporting a discharge electrode, a. discharge electrode comprising a plurality of sources of ionization located in a plane oppositely disposed to said surface, means for supporting an additional discharge electrode, an additional discharge electrode comprising a plurality of sources of ionization located in a second plane oppositely disposed to said surface, and means for maintaining said first plane and said second plane with an angle therebetween with said planes located nearer said surface than said electrode support means.

4. In an electrostatic coating apparatus, means for supporting a surface to be coated, a discharge electrode, means for supporting said discharge electrode in a plane oppositely disposed to said surface, a second discharge electrode, and means for supporting said second discharge electrode in a second plane intersecting the plane of said first electrode and being oppositely disposed to said surface. each of said discharge electrodes being closer to the surface to be coated than its associated supporting means.

5. In electrostatic coating apparatus, an electrode frame, an ionizing wire tensioner comprising a resilient strip, means for securing one end of said tensioner to said frame. the opposite end of said tensioner being reversely bent to provide a curved bearing portion and an extension having a slot therein, and an ionizing wire passing through said slot and over said bearing portion.

6. In electrostatic coating apparatus, an electrode frame, an ionizing wire, resilient means securing said :wire to said frame comprising a helical spring secured at one end to the frame and at its other end to said wire, and a shield about said spring.

7. In electrostatic coating apparatus, an electrode frame, a tension member comprising a resilient strip having an openin therein at one end, means for securing the opposite end of said member to said frame, one or more tabs disposed about said opening, and an ionizing wire passing through said opening and wound about said tab or tabs.

8. An apparatus comprising an electrode support, an electrode wire carried thereby, and means for maintaining said wire under tension including a link disposed in substantial alignment with said wire, connected at one end to said support, and having at its outer end a plurality of perforations through which the wire is laced.

9. In apparatus for coating a plurality of articles with liquid coating material, a discharge electrode having a plurality of sources of ionization distributed in a plane, a second discharge electrode having a, plurality of ionizing sources distributed in a second plane, electrode supporting means supporting said electrodes with their planes forming a dihedral angle, a conveyor for conveying the articles to be coated in succession through such dihedral angle and past said electrodes, means including a high-voltage source havin its opposite terminals connected respectively to said electrodes and to the articles moving past them and capable of creating an ionizing zone adjacent each discharge electrode, and means for discharging particled liquid coating material through said ionizing zones to acquire an electrical charge and be electrically urged toward the article for deposition thereon, said electrode supporting means \being located outside the dihedral angle through which the articles pass.

ROBERT H. STONE.

REFERENCES CITED Anderson Nov. 22, 1927 Ronsburg et a1. July 1, 1941 Number 

